Adherence to hormone therapy among women with breast cancer.

Background: Despite the excellent results obtained with hormone therapy, the long treatment period and the side effects associated with its use make patient adherence difficult. Moreover, certain aspects of health care can mitigate or exacerbate non-adherence. This study aimed to identify the factors associated with adherence to hormone therapy for breast cancer, with the goal of contributing to the reformulation of the care process and to improvements in outcomes.

Method: This was a retrospective longitudinal study based on secondary data. The study integrated and analyzed data from a cohort of 5,861 women with breast cancer who were identified in the databases of the Brazilian National Cancer Institute [Instituto Nacional de Câncer - INCA] and the Unified Health System [Sistema Único de Saúde - SUS]. All of the patients were treated at INCA, which dispenses free medication, and the follow-up period lasted from 01/01/2004 to 10/29/2010. The outcome of interest was hormone treatment adherence, which was defined as the possession of medication, and a logistic regression model was employed to identify the socio-demographic, behavioral, clinical, and health care variables that were independently associated with the variations in this outcome.

Results: The proportion of women who adhered to hormone therapy was 76.3%. The likelihood of adherence to hormone therapy increased with each additional year of age, as well as among women with a secondary or higher level education, those with a partner, those who underwent surgery, those who had more consultations with a breast specialist and clinical oncologist, and those who underwent psychotherapy; the effect for the latter increased with each additional consultation. Conversely, the likelihood of adherence was lower among patients at a non-curable stage, those who were alcohol drinkers, those who received chemotherapy, those who had undergone more tests and had more hospitalizations, and those who used tamoxifen and combined aromatase inhibitors.

Conclusion: This study shows that approximately a quarter of the women with breast cancer did not adhere to hormone treatment, thus risking clinical responses below the expected standards. It also identifies the most vulnerable subgroups in the treatment process and the aspects of care that provide better results.